What occurs when an electron is excited in a molecule?

When an electron is excited in a molecule, it transitions from a lower energy state to a higher energy state. This process often involves moving from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO). The excitation of an electron occurs when energy is absorbed, promoting it to a higher energy level where it is no longer bound to its original orbital.

This transition is fundamental in understanding molecular orbital theory, which describes how electrons occupy orbitals in a molecule. The HOMO contains the highest energy electrons, and the LUMO is the next available energy state that can accommodate an electron. This concept is crucial in various applications, including photochemistry, where the absorption of light can cause such excitations and lead to chemical reactions.

In contrast, the other choices do not correctly describe the typical process of electron excitation in molecular terms.